The subject matter disclosed herein relates to the optical measurement of light and, more particularly, to an optical sensor that performs three-dimensional, spatially-resolved optical measurements of the flame of a combustor of a gas turbine engine and to a system that utilizes the optical measurements to better control the combustion process.
Optical measurements of flame chemiluminescent light emission are routinely used in premixed gas combustors in gas turbine engines to determine various parameters such as energy or heat release rates and fuel-to-air ratios in such combustors. Placing wavelength filters in front of optical detectors is typically used to identify the partial contribution of the total light emission from each of specific excited-state species, such as OH*, CH*, C2* and CO2*. Ratios of the signals of one or more of these species can then be correlated in a known manner to various combustor parameters such as the fuel-to-air ratio, heat release rate and gas temperature. Previous applications of this measurement technique have used simple optical sensor arrangements and camera systems. A problem with these techniques and systems is their inherent limited spatial resolution. In complex combustion flows, the ability to make spatially resolved measurements in three dimensions is critical to optimizing system performance through improved control of the combustion process.
The use of exhaust temperature spread as a surrogate for combustor chamber-to-chamber variation in fuel-to-air ratio, heat release rate and gas temperature is adequate. However, results can be improved by using optical techniques to observe the flame in each combustor can. A primary issue with using optical methods in these situations has been that they typically provide limited line-of-sight information when what is preferably needed is three-dimensional, spatially-resolved information about the entire flame in each combustor can.